Parallel Feeders

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dvcraven0522

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I have attached a PDF of a one line diagram.

I am providing for parallel 750kcmil to a 1000 amp CT enclosure 1000'-0" distance. My question is if I provide 4 sets of 750kcmil to the CT cabinet am I required to provide the same quantity from the CT cabinet to the 1000 ampere MDP which is inside the building which has a distance of only 20'-0". I am thinking yes but, I thought I would post this and get your thoughts.

All of these feeders are fed via underground PVC.
 

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  • 21-09-29-Riverport-1 Elec-RP1 E1.0.pdf
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The different sections do not have to have the same size, quantity or characteristics. I would make the portion from the CT cabinet to the MDP just for the 1000 amps. 3 sets of 500s or 4 sets of 250 for example.
 
I agree with texie about the requirements.

All _parallel_ conductors must have the same characteristics, but different sections along the length of a circuit can have different characteristics.

As a design choice you might use the same 750s for the short section just to have fewer different parts to manage on the job, or you might chose smaller conductors that are easier to handle getting from the CT to the pull section.

Jon
 
Since you already have 750 kcmil Al I would stay with that. Since there's only 20' of length 3 sets of 750s (385 amps * 3 = 1155 amps) would work.
 
drktmplr12 said:
MDP-2 is not protected and presumably is the service entrance equipment based on the N-G bonding jumper. How do you disconnect power from MDP-2?
Click to expand...
MDP-2 would be under the 6 service disconnect rule. Right now there is only one shown but there is room for 5 more.
 
i'm not used to seeing it this way as I am primarily in industrial settings. reading the section more closely, I see it's not required that MDP-2 be protected. 408.36 exception 1 applies to exactly this arrangement.

From a design perspective, it seems more hazardous to rely on the transformer's bayonet fuse than having main OCPD, from an arc flash/incident energy perspective. I acknowledge that this is my bias creeping in.

thanks for educating me!
 
Thank you.
Again unrelated, I see this a quite often.
Maybe comment more in camp fire chat. I believe this may be the place for it.
 

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One item leads to another(conductor fill . Once sized correctly it may lead to undersized raceway. Especially when using FMC at the transformer.
May have to run that calculation to see if it applies to this install.
On a lighter side I was told once the 2ft piece of FMC attached to the EMT was a nipple on the 15 ft run.
Yes I do realize it says two and a half inch EMT no mention of FMC.
Been reading through the form rules and not sure where to comment further, maybe education. Just don't want to clog up this post with an unrelated issue.

Again thanks.
 
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